Electric furnace.



M. SHOELD.

ELECTRIC FURNACE.

APPLICATION FILEDJAN. 28, 191s.

1 ,274,794. Patented Aug. 6, 191&

hot escaping gas.

UNITED sTATEs PATENT oEEicE.

MARK SHOELI), OF CHICAGO, ILLINOIS, ASSIGNOR TO ARMOUB FERTILIZER WORKS, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Aug. 6, 1918.

To all whom t may concern.' Be it known that I, MARK SHoELD, a subject of the King of Sweden, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

My invention concerns electric furnaces and the production of desired chemical reactions thereby. While the invention has many broad features of novelty, it is of especial use in, but not necessarily limited to, the production of aluminum nitrid which requires a high degree of heat to effect the required chemical result. p

One object of the invention is the provision of a furnace of this type which will produce a substantially-uniform heat throughout a certain zone or section of the material treated and in which the electrodes will notbe consumed either electrically or chemically. A further feature of the new furnace is the assurance that, the gas used will be uniformly dispersed or distributed through the pieces of particles of solid material treated. .Another purpose of the invention is to so arrange the travel of the solid and gaseous materials that they will tend to confine the heat to a certain limited desirable zone; the gas being preliminarily heated by the hot solid material, and the solid material being initially heated by the A further purpose of the invention is the use of a lining for the furnace capable of withstanding the high temperatures necessary for an indefinite period without deterioration and protecting such lining in various ways to prevent its undue wear or impairment. Still another object is to so construct the furnace and use the material .treated that the latter shall prevent electric short circuiting.

In order that those skilled in this art may have a full and complete understanding of this invention and its various structural and functional advantages, I have illustrated a preferred embodiment of the same in the accompanying drawing throughout the views of which like reference characters refer to the same parts, and to which drawing reference should be had in connection with the'following detailed description.

In the drawing: 1

Figure 1 is a vertical section through the furnace, and

Fig. 2 is a horizontal section on line 2-2 of Fig. l.

The furnace comprises a Vstructure with a central vertical passage or chamber 10 octagonal in cross-section (Fig. 2), although its particular shape is immaterial so long as it is positioned substantially vertically to secure a corresponding feed of the material by gravity. Such passage or compartment at its central portion is lined with carbon bricks or blocks 11, 11, surrounding which is a ring 12 of black-bricks of speclal composition, and outside of these are lire-bricks 12 which also form the upper flared portion 14 of the passageand a lower portion 15 thereof. Outside of such firesbricks isa layer or stratum of silocel bricks 16, and around this is an exterior metal shell or casing 17 which also covers the top and bottom of the furnace, the whole being supported on concrete pillars or posts 18, 18.

At its top, this outwardly-widening or flaring chamber divides into two diverging branches 19 and 20 through which the material to be treated is introduced into the furnace, such material being ordinarily in the form of briquets, composed of finelydivided alumina and carbon held together with a suitable binder. Each such branch has an upstanding gas outlet 21 and a poke hole 22.

Disposed centrally inv passage 10 is an upright, graphite electrode 23 extending up- The companion electrode of the circuit comprises an encircling graphite ring 26 located substantially in the middle of the furnace with portions of the carbon-lining both above and below it, and composed of a series of graphite-blocks wedged together into adequate physical and electrical contact. Such ring is connected tothe electric circuit referred to by means of two, opposite, spaced, graphite conductors 27- and 28 maintained in adequate contact with the ring and each supplied outside of the furnace with a clamp 29, cooled by a spray 30, fastened to an electric wire or cable 31. Where these electrodes 27 and 28 pass through the metal-shell and also around the clamp 2l, I provide a suitable supply of asbestos cement 32 as a sealing means.

In its lower portion, the furnace has a tube or conduit 33 directly connected-to and beneath the main passage to the furnace through which pure nitrogen, or impure nitrogen containing a small percentage of carbon monoXid, is introduced into the furnace under pressure. p

To assist in cooling the furnace, the firebricks of its upper part may have embedded in them a cooling water-coil 33.

In the operation of the improved appliance the briquets referred to are introduced continuously or substantially continuously into the two branch passages 19 and 20 and the product is continuously removed from the bottom of the furnace, both without permitting an escape of the gas. It has been deemed unnecessary to illustrate these details as they are well known and may be of any suitable construction.

In carrying out the process by this particular apparatus, it may loev remarked that the briqueted solid material or mixture will not, when cold, permit a passage of electric current of' appreciable volume between the center electrode and its companion ring electrede. In other words, the current will not be initiated or established. It is, therefore, necessary to prime the apparatus by using graphite to start the current flowing. Such current then, during the constant gradual descent of the briquets, in passing through such material from the one electrode to the other substantially-uniformly heats the material by reason of the resistance which it offers to the passage of the current flow. Such heating, however, is limited to the region of the electrodes because of the greater resistance of the carbon and the sufficiently great resistance of the relatively-cool incoming or downflowing briquets. Nor does such electric current in its heating effect travel downwardly even though some of the carbon lining and the solid material being treated are below the ring contact. This is due to the fact that the relatively-cool ascending column of as keeps the temperature of the briquets su ciently low, that is to say, keepsIv the resistance of the material high enough, to prevent the current from passing at this point.

Inasmuch as the descending column of material travels downwardly in a vertical path and the gas passage is vertical, such gas distributes itself uniformly through the evenly heated briquets at the plane of the electrodes, thus bringing about a thorough and complete chemical reaction. The descending incoming body of cocl material and the ascending incoming body of cool gas, both tend to confine the heated currentcarrying zone to the plane or place of the electrodes, thus desirably centrally confining the heat. Inasmuch as the inner electrode is entirely surrounded by the briquets, the latter prevent short circuiting between the electrodes and there is complete assurance that the current will pass equally throughout such material and heat it practically uniformly.

It will be easily understood that the outer ring electrode is adequately suppo-rted and not subject to damage or injury, and that since the center electrode is arranged or disposed vertically itis freed from strains which might otherwise tend toward its injury. Furthermore, since no electric arc is employed, there is no electrical consumption of the electrodes, and since the gas employed has no oxidizing effect there is no chemical deterioration of the electrodes. Furthermore, a slight excess of carbon is used in the briquets so that this may be considered as a safety measure with respect to undesirable chemical effects on the carbon lining.

While I have herein presented one prei ferred and desirable embodiment of the invention, it is to be understood that the latter is susceptible of a variety of embodiments and that many minor mechanical changes may be incorporated in the structure presented without departure from the substance l electricity therethrough, said contents completing the electric circuit between said electrodes, and means to cause the material to be treated to pass between said electrodes, substantially as described.

2. In an electric-furnace of the character described, the combination of a furnacebody, a carbon-lining for the heat-chamber thereof, electrodes of electrical conductivity greater than that of said carbon-lining arranged to contact with the contents of said heat-chamber and direct a current of electricity therethrough, such contents completing the electric circuit between said electrodes, and means to cause the materlal to be treated to pass between said electrodes, substantially as described.

3. In an electric-furnace of the character described, the combination of a furnacebody, a carbon-lining for the heat-chamber thereof, graphite electrodes of electrical conductivity greater than that of said carbonlining arranged to contact with the contents of said heat-chamber and direct -afcurrent of electricity therethrough, such contents completing the electric-circuit between said electrodes, and means to cause the material to be treated to pass between said electrodes,

substantially as described.

4. In an electric-furnace of the character v described, the combination of a furnacebody, an electrically-conductive limn there- A for, and electrodes arranged to sen a current of electricity through an intermediate portion only of the contents of said lining and of electrical conductivity greater than that of said electrically-conductive lining, substantially as described.

5. In an electric-furnace of the character described, the combination of a furnace-body having a vertical passage therethrough, an outer substantially-horizontal ring electrode disposed exteriorly of and adapted to contact with the material to be treated in said furnace body, a center electrode supported from above and projectin down into the plane of said ring electro e, means to feed the material to be treated downwardly between said electrodes, and means to Send a current of gas through the material between said electrodes, whereby said interposed'material may be heated by an electric current between the electrodes and be subjected simultaneously to the action of the gas, substantially as described.

6. In an electric-furnace of the character described, the combination of a furnace-body having a vertical passage therethrough, an outer substantially-horizontal ring electrode disposed exteriorly of and adapted to contact with the material to be treated in said furnace-body, a center electrode supported from above and projectin down into the plane of said ring electro e, means to feed the material to lbe treated downwardly between said electrodes, and means to send a current of gas upwardly through the material between said electrodes, whereby said interposed material may be heated by an electric current between the electrodes and Abe subjected simultaneously to the action of surrounded by and in contact with the matel rial to be treated, an outer graphite-rin electrode disposed exteriorly of and adapte to contact with the material to bel treated, and means to send a current of gas upwardly through said passage and the material interposed between saixd electrodes, whereby said material may be simultaneously subjected to the action of the gas and to a heating current of electricity through said electrodes, substantially as described.

8. In an electric-furnace of the character described, the combination of a furnacebody having a vertical passage therethrough, an electrically-conductive lining for said passage, a vertically-disposed electrode extending into the cavity of said body and adapted to be surrounded by and in contact with the material to be treated, an outer ring electrode disposed exteriorly of and adapted to contact with the material to be treated, and means to send a current of gas upwardly through said passage and the material interposed between the electrodes, whereby the material may be simultaneously subjected to the action of the gas and to a heating current of electricity through said electrodes, said electrodes bein of greater electrical conductivity than sai lining, substantially as described. A

9. In an electric furnace' of the character described, the combinationnf a furnace body having a vertical passage therethrough, a carbon-lining for said passage, a verticallydisposed graphite electrode extending into the cavity 4of said body and adapted to be surrounded by and contact with the material to be treated, an outer graphite ring electrode disposed exteriorly of and adapted to contact with an intermediate section only of the material to be treated, and means to send a current of gas upwardly throu h said passage and the material interposed etween said electrodes, whereby said material may be simultaneously subjected to the action of the gas and to a heating current of electricityA through said electrodes, substantially as described.

10. In an electric-furnace of the character described, the combination of a furnace-'body having a vertical passagetherethrough, an electrically-conductive 1min for said passage, a vertically-dis osed eectrode extending into the cavit o said body and adapted to be surroundedY by and contact with the material to be treated, an outer ring electrode disposed exteriorly of and adapted to Contact with an intermediate section only of the material to be treated, and means to send 5 a current of gas upwardly through said passage and thematerial interposed between said electrodes, whereby said material may be simultaneously subjected to the action of the gas and to a heating current of electricity through said electrodes, Said electrodes 10 being of greater electrical conductivity than Said lining, substantially as described.

MARK SHOELD. 

